What are trans fats? While some trans fat (21 percent according to FDA) appear in milk and meat naturally (these don’t appear to be harmful), most are formed when hydrogen is added to oil in a process called “hydrogenation.” This process is used to turn liquid oil into the familiar white creamy vegetable shortening and some of the hard margarines. These products are then used, not just at home, but in food manufacturing to produce crackers, cookies, snack foods and more. In addition, most restaurants are still using hydrogenated shortening in their deep fat fryers.

Why do manufacturers make hydrogenated products? Back in the 1970s and ’80s, when Americans became educated about the harmful effects of using animal fat, food manufacturers and restaurants made the switch from lard to vegetable oils. At that time, liquid oils proved to be unstable. Baked goods went rancid quicker; frying oils could only be used for short periods of time before being trashed (many restaurants filter their frying fat, but use the same fat for a week or more). Manufacturers found out that when they added hydrogen to the oil, it resulted in a more stable product.

Moderate amounts of fat in the diet are considered healthy. Fats are important for growth and maintenance of the body, aid in the absorption of the fat soluble vitamins (A, D, E and K), add flavor to foods and fill you up. A healthy diet includes 20 to 35 percent of all your calories from fat. But the type of fat is important.

What are the different types of fat? Monounsaturated fats are considered the healthiest since they help to lower your serum cholesterol. These are found in foods such as walnuts, almonds, canola oil, avocados and olive oil. Polyunsaturated fats (including soybean, sunflower oil and corn oil) can lower cholesterol as well, but some of the effect is coming from a lowering of your good (HDL) serum cholesterol. Your total intake of saturated fats (found in animal fats, coconut oil and palm kernel oil) plus trans fats should be limited to less than 10 percent of your total calorie intake.

Why are trans fats harmful? Like saturated fats, trans fats have been found to raise your serum cholesterol levels—some research hints that trans fats raise cholesterol even more than saturated fats. Where are trans fats found? You’ll find high levels of trans fats in most deep fat fried foods including French fries, fried fish, fried chicken and donuts. In addition, crackers, cakes, cookies, chips, margarine, popcorn and nutrition bars still contain high levels of trans fats. Keep in mind, that most trans fat-free products are not really free; products containing fewer than 0.5g of trans fat per serving are allowed to round down to “zero” under the labeling laws. Are you eating just one serving?

Where can I find trans fat-free products in the grocery store? The 2006 labeling law makes it easy to check; this law requires most grocery store products to state trans fat levels in their nutrition information. Many food manufacturers have already made the switch. These include Kraft Oreos and Frito Lay products including Lay’s, Doritos, Cheetos and Tostitos. But, remember trans fat-free does not mean fewer calories. Most trans fat-free products have exactly the same amount of fat and calories as the original.

Dr Jo is a PhD nutritionist and registered dietitian. Like you, she’s busy and is constantly on the search for healthy menu options (in restaurants) and grab ‘n go products (in the supermarket and convenience stores). She’s the author of three books: Dining Lean, Dr Jo’s No Big Deal Diet, and How to Stay Healthy & Fit on the Road.